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Topic: A beginners first engines (Read 3057 times)

Some who replied to my introductory post requested photos of the engines I had built before discovering this forum. I hope this is the right place and format. Actually my second engine, photo of the first later, if picture attaching is ok. Found many posts on how to do it, so I hope it works. Will not impress the experts, but I was proud of my first efforts.

A double acting oscillating engine (wobbler) with my own design Meths fired boiler, and fitted with an exhaust separator and temperature measuring points for boiler, superheater outlet/ engine inlet and engine outlet. The white patch on the flywheel is the reflector for a digital non-contact tachometer. A small DC brushed motor driven as a generator provides a small load to a resistor. I must apologise to you, Don for the finish, your magnificent E & A beam engine has inspired me to buy some rotary brass brushes, now for some elbow grease! I will be aiming higher for future builds.

The principle for these engines is in so many books, who do I credit? My own layout and dimensions allowed me to make the size I wanted (12 mm bore x 16 mm stroke) with a rationalised selection of material sizes and necessary tooling. Cylinder bored off centre in the four jaw to give extra thickness for the pivot insert. No mill available at this stage. Lots more off centre turning for the lubricator. Many thanks to my brother for his helpful and much needed instruction on machining and silver soldering.

I know, some would like to see the test results, a clear set is already on my "to do" list.

Hi MJM ( name ? ), thanks for posting the picture of the complete small steam plant, reminds me of fun with the commercial Mamod oscillator plants that we used to have as kids years ago in the UK. ( And a burnt finger, meths flames aren't easy to see in sunlight... ) Be pleased to see pictures of your slide valve engines. Dave

I have selected my first engine as my avatar, a single acting oscillator with a soldered head. Same bore, stroke and frame size so the first and second are interchangeable in the first steam plant, which is a simple Mamod style pot without any water tubes as Dave has noted, though it has a superheater coil.

Here is my first slide valve effort. A typical mill engine style, similar to many published designs, but not copying any one in particular. I kept to 12 mm bore, but lengthened the stroke to 20 mm, just seemed to look better proportioned for this style. Bar stock, some key steel and a piece of plate for the base. I want to dress up the boiler before showing it, tin plate cut from a large coffee tin works for trial runs but does not look appropriate here. So some sheet brass work is now high on the work list.

And Don, yes, proud to have progressed this far, but I hope to pick up a few tips on finishing them off. That little black oscillator of yours sets a standard, but oh, so far to go. Your models are truly inspiring.

Thanks for showing the picture of your slide valve engine, MJM. Nicely thought out little engine. These small engine projects are a good way into the model engineering hobby - working towards a model that interests you personally, which doesn't bog you down in too much work to see it completed, and learning many essential processes meanwhile. Cheers, Dave

This is my most recent engine. I have attempted to design the a joy valve mechanism, but replaced the curved sliding link with a swinging lever after the Hackworth-Marshall idea. Does that make it a Joy-Marshall? I am sure it will not be original, but I have not seen any designs on this principle.

It started out as some aluminium links to prove the concept, but then it needed a crank and conrod, a cross head, and so it grew like Topsy and became a working, if not terribly elegant engine. The diagonal layout is pointing towards a concept to install in a paddle steamer. And the valve location gave a very short engine in the crankshaft direction so the hull does not have to be too wide. I wanted to prove the concept before I had a good go at a full two cylinder model.

Using this as an experimental test engine. Main issue is the number of links which give too much opportunity for wear and lost motion, but it runs both directions and like the mill engine, gives me the opportunity to learn about and practice valve setting. Perhaps I should try an alternative Hackworth-Marshall for comparison. A modified frame which does not hide so much of the motion would also be an improvement.

Hi Gary, thanks for that, I am glad you like it. And it is good to see that people look through old threads,mothers is so much interesting and valuable information there,Ma real treasure trove.

That one was an experiment to test the valve mechanism design, 3-D solid work, my style, then continued to grow to a complete engine. But it runs well and the reversing gear all works. Balance is not as good as I would like, but has the advantage that it rarely if ever stops on top or bottom dead centre, so at least unloaded, it seems to always self start.

OK Thomas, you caught me out. I thought I had sneaked through on that one. Looks like I will have to work out how to post a video, which file type for the movie etc. It's on the list, but as Chuck says, so many projects, so little time. But definitely in time for my next engine.

Hi Zephyrin, thank you, I very much appreciate your comment. You raise a valid point about the Hackworth part of my description. The motion is very much a Joy valve motion, but with pinned levers replacing the slide link. I had seen a similar idea in a book, which one I can't recall now, but it gave me the idea to replace the curved sliding link with levers pin jointed at the centre of curvature of the curved link, and somehow associated it with the Hackworth gear in my mind. I felt that I could make pinned joints with much less friction than a poorly made curved slide.

Never the less, I do believe the valve events are assymetrical as you say, (confirmed by careful observation with the steam chest cover removed, but I consider the experiment a success in that the engine runs quite well in both directions, at least when unloaded. I still need to build some sort of load or better still a torque meter/brake to do some load testing. It does accurately follow the Joy valve motion, though my calculation of the link lengths may not be optimum for lap and lead, as you might expect from a beginner. I believe a new valve will improve it a little, as some of the dimensions are not quite right for the port spacing.

The number of links meant that my inaccuracies added up, and it is difficult to get at some points for lubrication. So for practicality for say a model boat, I think I will go for the classical eccentric. I am interested in the piston valve version of the Marcher engine as possibly the simplest way for practical and reliable radio controlled operation with only one eccentric. I need to build a piston valve engine to test and develop my skills, however there is another slide valve engine from castings on the list to try first. It will be my first casting experience, so I am carefully taking note of Jo's advice on the fondling that must occur first. And also all hints on machining the bronze castings. They look too nice for me to want to risk spoiling them.

Come to think of it, I could follow John Berrinat's example and make a piston valve chest dimensioned to be interchangeable with the slide valve as designed. I will think more about that.